Electronic devices in a premises that monitor safety, security, climate control, etc., are often mounted on walls in the premises and require power. Users typically prefer not to run wires to the devices from outlets for power. However, if batteries are used to power the devices, the user must periodically change the batteries. In some circumstances a device may be nonfunctional during a critical time due to lack of power from a dead battery that has not yet been changed. If, instead of batteries, a custom power delivery system is used involving splicing wires behind walls to power the devices, then professional installation is often required, which can be expensive for the user.